Number of modes in optical fiber

[says]

Homework Statement

Can a single mode fiber become multimode if the wavelength of the light passed through it is small enough?

I put a HeNe laser (633nm) through what I thought was a single mode fiber. If it's supposed to operate at 1300nm, then would a low wavelength of 633nm cause multiple modes in the single mode fiber?

Homework Equations

number of modes = operational wavelength / wavelength used

The Attempt at a Solution

number of modes = 1300nm/633nm = (approx.) 2 modes?

I'm not sure why my image isn't showing a uniform mode / pattern.

 

[tech99]

Homework Statement

Can a single mode fiber become multimode if the wavelength of the light passed through it is small enough?

I put a HeNe laser (633nm) through what I thought was a single mode fiber. If it's supposed to operate at 1300nm, then would a low wavelength of 633nm cause multiple modes in the single mode fiber?

Homework Equations

number of modes = operational wavelength / wavelength used

The Attempt at a Solution

number of modes = 1300nm/633nm = (approx.) 2 modes?

I'm not sure why my image isn't showing a uniform mode / pattern.

Maybe you have a multimode fibre?